From DE 19782074 it is known that plastic films or foils can be fused to one another by means of a laser for the purpose of producing packages or bags. In so doing, a light absorbing foil itself can be heated for such fusion, or a component can be heated, which is in mechanical contact with at least one of the foils.
For packing fresh food such that the longest possible shelf life is accomplished, it will often not suffice to only close the package in an air-tight manner. The demands that have to be met by the atmosphere in the closed package are here much higher. In order to achieve very low residual oxygen values in the package, it is necessary to generate a vacuum of e.g. less than 10 mbar or to evacuate the package and/or flush it with gas, preferably with nitrogen and/or a gas mixture containing carbon dioxide, before the package is closed.
DE 19782074 does not provide any information how packages with a modified atmosphere could be produced and sealed, respectively, by means of a laser.
Normally, packages with a modified atmosphere are, e.g. on deep-drawing packaging machines, evacuated and/or flushed with gas through a closed chamber in the sealing station and the foils are pressed together and fused to one another by means of a permanently heated sealing plate so as to form a sealing seam that is closed all around. A high expenditure of energy is here necessary for permanently maintaining the sealing plate in a heated condition at the temperature required, and, for changeover operations, a cooling time required for cooling down has to be observed.